Circulatory System Structure and Blood Flow Dynamics (3B) Practice Test

During acute exercise (cardiovascular adaptation), a subject’s heart rate rises from 60 to 150 beats/min. Echocardiography shows stroke volume increases from 70 to 90 mL/beat. The central physiological principle is cardiac output relationship: $CO = HR \times SV$. Homeostatic control maintains cerebral perfusion by stabilizing MAP near baseline via changes in vascular tone. Based on the passage, which conclusion about systemic blood flow is most consistent with these changes?

In a vascular imaging study, two arterioles of equal length were compared: Arteriole A had radius $r$, and Arteriole B had radius $2r$. Blood viscosity and pressure gradient were similar, and flow was laminar. The central principle is that resistance varies inversely with $r^4$, making small radius changes powerful for perfusion homeostasis. Which outcome would be expected when comparing the two vessels?